[ELF2/LinkerScript] Fix OUTPUT_FORMAT directive parsing

Differential Revision:	 http://reviews.llvm.org/D13668

llvm-svn: 250106
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index f255da3..4d05e10 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -212,6 +212,14 @@
   // Error checking only for now.
   expect("(");
   next();
+  StringRef Tok = next();
+  if (Tok == ")")
+   return;
+  if (Tok != ",")
+    error("unexpected token: " + Tok);
+  next();
+  expect(",");
+  next();
   expect(")");
 }